Contrasting Worm Gear vs. Bevel Gear

For design engineers and equipment manufacturers, choosing between worm gears vs. bevel gears can make a huge impact on efficiency and operating cost. In this article, we'll explore the key benefits of worm and bevel gears to help you determine which may work best for your application.

Advantages and Disadvantages of Worm and Bevel Gears

Worm gears and bevel gears are two types of gears that are commonly used to transfer motion at a right angle. Conveyors, cranes, lifts, mixers, blenders and many other applications rely on either worm or bevel gears to drive their operation.

Worm Gears

A worm gear set consists of two parts, a worm gear and a worm wheel. The two gears are often made out of two different materials (a steel worm and a bronze worm wheel). Worm gears use a sliding action (rather than a rolling action) and transfers motion at a right angle, as illustrated in the image below.

Worm gear

Worm gears offer their best benefit when a large ratio is required, as a worm gear can achieve a larger total ratio with less gear sets. This means a smaller, less expensive gearbox can be used which is appealing for smaller machinery or when trying to keep installation costs low. Typically the highest ratio a worm gear set can achieve is about 100:1.  Some worm gear sets cannot be back-driven which is advantageous in applications where braking is required. Worm gears can be used as a secondary locking or braking system to stop components from moving in the reverse direction.

Due to the friction caused by the sliding contact of the gears, worm gears have high operating temperatures and low efficiency. In addition, since the worm wheel is often made of bronze, which is a softer metal, the worm wheel will wear. While this quick wear is a disadvantage, the bronze worm wheel helps to reduce the friction from the sliding contact to positively impact the efficiency.  

Bevel Gears

There are four types of bevel gears; spiral, straight, zerol and skew tooth. NORD Drivesystems' bevel gearboxes use spiral bevel gears. Bevel gear sets are composed of two parts, the bevel pinion and bevel gear which transfer motion at a right angle. 

Spiral bevel gears use gear teeth that are angled and spiraled. With this design, as the gears rotate, the entire face width of the mating teeth don't contact simultaneously and more teeth are in contact at one time. This results in a quite operating noise and increased torque capacity. The quiet operation is particularly beneficial in environments such as theaters or airports

Spiral helical bevel gear set

The rolling action of bevel gears is extremely efficient (98.5%) compared to the sliding action of worm gears. NORD bevel gears operate with a microscopic oil film between the gearing which results in no metal to metal contact which improves efficiency and results in essentially wear free gearing. 

The disadvantages of using bevel gears come with the cost. Bevel gears are manufactured in pairs. This means not only are they more expensive to make;  maintenance and repairs often require the replacement of both gears. In addition, in order to get the most efficiency out of bevel gear sets, they must be precisely positioned and assembled. Bevel gears also have a limited ratio range (typically 6:1 max per set), so more gears are required in a gear train in order to achieve a higher total gear ratio.

Which Gear Technology is Right For You?

Contrasting the advantages and disadvantages of worm vs. bevel gears can help you determine which system is right for your application. NORD Drivesystems features a large portfolio of gear motors, including worm and helical bevel gears, that allow you to purchase cost effective solutions and conduct operations at the highest efficiency. 

Our integrated gearmotos are adaptable to a wide variety of applications in almost any industry around the world. We work closely with engineers, purchasers and machine manufacturers to design the gear solutions that perfectly fits their unique needs.

Connect with a NORD Drivesystems representative today to learn more about how our gear solutions can help your applications!

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Machine Design: http://machinedesign.com/whats-difference-between/what-s-difference-between-spur-helical-bevel-and-worm-gears